Address information setting method and mobile terminal

ABSTRACT

The invention provides an address information setting method such that when home agent information such as an address of a home agent, which is basic information for activating mobile IP protocol processing, is acquired, it is made possible to perform communication that satisfies requirements desired by a user or an application by starting mobile IP protocol processing using home agent information acquired according to an instruction of a user. In addition, it is possible to reduce the work burden on a user for making settings and provide a mobile terminal with high convenience by automatically acquiring home agent information on a link at a time specified by the user.

TECHNICAL FIELD

The present invention relates to an address information setting methodfor a mobile terminal, which carries out an Internet protocol, inparticular, a mobile IP procedure, and the mobile terminal.

BACKGROUND ART

Mobile IP is one of methods for mobility management in the Internetsystem. The Mobile IPv4 is standardized by the RFC3220 (IP MobilitySupport). The Mobile IPv6 is still being standardized in the Internetdraft draft-ietf-mobileip-ipv6 (Mobility Support in IPv6). Theseprotocols allow a mobile terminal to perform communication using thesame address even when the mobile terminal moves among differentnetworks.

In the Mobile IPv6, when a mobile terminal has moved away from a homelink, the mobile terminal acquires prefix information of the link towhich the mobile terminal has connected, from network informationtransmitted by an access router apparatus of the link, and therebygenerates a care-of address that the mobile terminal uses in the linktemporarily. Thereafter, the mobile terminal transmits a binding updatemessage to a home agent to register the care-of address as the primarycare-of address to the home agent which has home link for the mobileterminal. After receiving the binding update message from the mobileterminal, the home agent creates or updates a binding cache entry thatassociates a home address and the care-of address.

The home agent refers to the binding cache, and receives as a proxy apacket which has been transmitted to the home address of the mobileterminal. Then, the home agent encapsulates the packet received andtransfers the encapsulated packet to the care-of address of the mobileterminal. The mobile terminal decapsulates the packet transferred by thehome agent and extracts the packet addressed to the home address of themobile terminal.

Conventionally, as a setting method for a mobile terminal in this field,for example, there is a setting method described in JP-2000-22708.

FIG. 17 is a diagram of a conventional mobile terminal described inJP-2000-22708.

In FIG. 17, a mobile IP managing unit 1025 determines whether the moduleshall be worked, in accordance with an instruction from an instructioninterface 1018. In other words, when the mobile IP managing unit 1025receives a setting input by a user through the instruction interface1018, operation of the mobile IP processing unit 1015 is enabled. Thus,An address converting unit 1023 changes the transmission source addressof a transmitted packet to be transferred to a device driver 1016 by anIP processing unit 1014, or an encapsulation processing unit 1022applies encapsulation processing to this transmitted packet. Inaddition, the address converting unit 1023 changes the destinationaddress of a received packet transferred from the device driver 1016 tothe IP processing unit 1014, or the encapsulation processing unit 1022applies decapsulation processing to this received packet. Moreover, themobile IP managing unit 1025 controls an input switch 1021 or an outputswitch 1024 to thereby decide whether transmitted/received packets arepassed through the address converting unit 1023 or through theencapsulation processing unit 1022. This makes it possible to realize amobile IP function without changing the existing IP processing unit1014.

However, in order to activate mobile IP protocol processing, it isnecessary to set information, such as the address of a home agent orhome address in the mobile terminal by some means.

For this purpose, there is a method by which a mobile terminal acquiresinformation on a home agent from a DHCP server on a network using DHCP(Dynamic Host Configuration Protocol), which is a general protocol forallocating an IP address to a mobile terminal and notifying the mobileterminal of information on network servers and the like. When the mobileterminal acquires the information regarding the home agent from the DHCPserver, the mobile terminal automatically sets the information asparameters of the mobile IP protocol and starts protocol processing.

However, in the conventional method of acquiring and setting home agentinformation using DHCP, a problem described below occurs in anenvironment in which the mobile terminal can arbitrarily select the homeagent to which it will belong, from among plural home agents.

In general, a mobile IP service is provided in an office together with aVPN (Virtual Private Network). Only employees are permitted to access acompany network from locations outside the company such as business tripdestinations and homes of the employees. Terminals of the employees aremanaged with one IP address (home address) for each. Consequently, themobile IP service realizes improvement of operating effectiveness whilekeeping security of communication. Therefore, the home agent is arrangedtogether with a VPN gateway function, and a communication path betweenthe home agent and the terminal is protected by a high security systemconsisting of strict authentication and powerful encryption. On theother hand, since it is important to attain improvement of user trafficprocessing efficiency with respect to managing of plural terminals, ahome agent provided by an ISP performs encryption of a control messagefor binding update and the like but does not always perform encryptionof user data. Under such circumstances, when a user attempts to transmitan important business file to a company by electronic mail from a publicnetwork such as a hot spot that the user calls on at a business tripdestination, home agent information is automatically acquired using DHCPfrom the ISP to which the user has the subscription soon after theterminal to be connected to the network. Therefore, business data whoseconfidentiality must be secured is sent onto the public network in anunencrypted state. This may lead to a significant loss for security.

DISCLOSURE OF THE INVENTION

It is an object of the invention to provide an address informationsetting method that makes it possible to choose communicationenvironments that satisfies requirements desired by a user or anapplication when home agent information such as an address of a homeagent, which is basic information for activating mobile IP protocolprocessing, is acquired. It is another object of the invention to reducethe work burden on the user for making settings and provide a mobileterminal with high convenience.

The invention provides an address information setting method for amobile terminal that carries out a mobile IP procedure. The addressinformation setting method separates the acquisition operation for homeagent information and the setting operation for home agent information,judges after the acquisition operation whether protocol processing shallbe made to reflect the acquired information, and causes the mobileterminal to start the setting operation according to the result of thejudgment. In addition, the address information setting method isconstituted so that in response to a trigger given by a user, search ismade, from among the routers on the links to which the mobile terminalis connected at that time, for the home agent to be assigned to thatmobile terminal, the address of the home agent is stored, and an addressgenerated from a prefix distributed by the selected home agent is storedas the home address.

This makes it possible for the mobile terminal to be assigned the homeagent chosen by the user from among plural home agents after basicinformation required for carrying out a mobile IP protocol is acquired.It is also possible to acquire and set address information at a timedesignated by the user to reduce the work burden of manual setting bythe user and improve the convenience of the mobile terminal.

An address information setting method according to a first aspect of theinvention includes: a step of detecting a trigger from a user; a step,performed after the trigger is detected, of selecting a home agent tomanage a mobile terminal from among routers to which the mobile terminalis connected a step of generating a home address from the prefixdistributed by the selected home agent; and a step of carrying out amobile IP procedure using the selected home agent and the generated homeaddress.

This makes it possible to automatically acquire and set basicinformation which is required for carrying out a mobile IP protocol, atthe time designated by the user, thereby reducing the work burden ofmanual setting by the user and improving convenience.

An address information setting method according to a second aspect ofthe invention further includes a step of acquiring, when the trigger isdetected, router information from a network to which the mobile terminalis connected.

This makes it possible to perform accurate information setting on thebasis of router information collected on a real time basis.

In an address information setting method according to a third aspect ofthe invention, a home agent is selected from among routers whose flagindicating that it is a home agent is on, this flag included in acquiredinformation regarding the routers.

This makes it possible to secure compatibility with the conventionalsystem utilizing existing information, and improve communicationefficiency by selecting a home agent suitable for the application or thelike being run on the mobile terminal.

In an address information setting method according to a fourth aspect ofthe invention, in the selection of a home agent, from among the routerswhose flag is on, a predetermined number of routers are selectedaccording to a preferenceing defined in advance, in order from the onewith highest priority.

This makes it possible to secure compatibility with the conventionalsystem and, in selecting a home agent, realize optimization of systemprocessing load distribution by referring to priority information thatthe home agents set taking into account their processing loads.

In an address information setting method according to a fifth aspect ofthe invention, a home agent is selected arbitrarily from among therouters whose flag is on. This makes it possible to eliminate anincrease in load caused when one home agent manages a large number ofmobile terminals, instead assigning an equal number of mobile terminalsto all home agents, which makes it possible to optimize the load of theentire system.

An address information setting method according to a sixth aspect of theinvention further includes a step of acquiring from the user selectioncriteria for selecting a home agent from among the routers whose flag ison. In the step of selecting a home agent, the home agent is selectedaccording to these criteria. This makes it possible to select a homeagent according to the preferences of the user of the mobile terminal.

An address information setting method according to a seventh aspect ofthe invention further includes a step of notifying the user when theselection of a home agent is completed. This makes it possible to relaxlimitations on movements of the user by notifying the user thatinformation setting is completed.

In an address information setting method according to an eighth aspectof the invention, the selection of a home agent is performed usingrouter information acquired during a time period designated by the user.Since the user designates the period in which the information setting iscarried out, it is possible to relax limitations on movements of theuser which are present in the case where the information setting periodis uncertain.

A mobile terminal according to a ninth aspect of the invention includes:an input unit through which a user inputs a trigger for settinginformation regarding a home agent; an information setting unit thatselects a home agent to manage the mobile terminal from among therouters to which the mobile terminal is connected when the mobileterminal receives the trigger, and sets the address of that home agentand the home address, which are generated from a prefix distributed bythe home agent, as information regarding the home agent; and mobile IPprocessing means that carries out a mobile IP procedure using theinformation regarding the home agent.

This makes it possible to automatically acquire and set basicinformation which is required for carrying out the mobile IP protocol,at a time designated by the user to eliminate the burden of manualsetting by the user and improve convenience.

A mobile terminal according to a tenth aspect of the invention includes:a transmission unit that, when a trigger from the input unit isreceived, transmits a router information request message for requestingrouter information from a network to which the mobile terminal isconnected; and a receiving unit that receives router informationresponse messages that are responses to the router information requestmessage. The information setting unit selects a home agent to manage themobile terminal from among the routers that have transmitted the routerinformation response messages.

This makes it possible to perform accurate information setting on thebasis of router information collected on a real time basis.

In a mobile terminal according to an eleventh aspect of the invention,the information setting unit selects a home agent from among routerswhose flag, indicating that the router is a home agent included in therouter information of the router information response messages, is on.

This makes it possible to secure compatibility with the conventionalsystem by utilizing existing information and improve communicationefficiency by selecting a home agent suitable for the application or thelike being run on the mobile terminal.

In a mobile terminal according to a twelfth aspect of the invention, theinformation setting unit selects, from among the routers whose flag ison, a predetermined number of routers according to a preference definedin advance, in order from the one with highest priority.

This makes it possible to secure compatibility with the conventionalsystem by utilizing existing priority information and optimize systemprocessing load in selecting a home agent, by referring to selectionpriority information that is set taking into account the processing loadof the mobile terminals.

In a mobile terminal according to a thirteenth aspect of the invention,the information setting unit selects a home agent arbitrarily from amongthe routers whose flag is on. This makes it possible to eliminate anincrease in a load, which is caused when one home agent manages a largenumber of mobile terminals, assigning an equal number of mobileterminals to all home agents and thus making it possible to optimize theload of the entire system.

In a mobile terminal according to a fourteenth aspect of the invention,through an input unit the user enters selection criteria for theselection of a home agent to be performed by the information settingunit, and the information setting unit performs the selection of a homeagent on the basis of these criteria. This makes is possible to select ahome agent according to the preferences of the user of the mobileterminal.

In a mobile terminal according to a fifteenth aspect of the inventionincludes, the input unit may be a soft key on a screen, a button set ina main body, or a switch set in the main body. This allows the user tomake the timing setting conveniently.

A mobile terminal according to a sixteenth aspect of the inventionfurther includes a display unit that notifies the user that the settingof information on a home agent is completed. This makes it possible torelax limitations on movements of the user by notifying the user thatinformation setting is completed.

In a mobile terminal according to a seventeenth aspect of the invention,the input unit designates the time period in which the information on ahome agent is set, and the information setting unit performs settingsrelating to the home agent only in this period. Since the userdesignates a period in which information setting is carried out, itpossible to relax limitations on movements of the user which are presentin the case where the information setting period is uncertain.

In a mobile terminal according to an eighteenth aspect of the invention,the time period is a period in which the soft key, the button, or theswitch used as the input unit is in the state ‘ON’. Since the userdesignates the period in which information setting is carried out, it ispossible to relax limitations on movements of the user which are presentin the case where the information setting period is uncertain.

As described above, according to the address information setting methodof the invention, it is possible to perform communication that satisfiesrequirements desired by the user or the application, when home agentinformation such as the address of a home agent, which is basicinformation for activating mobile IP protocol processing, is received.In addition, the work burden on the user for making settings is reducedand convenience is improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing a first constitution of a mobile terminalaccording to a first embodiment of the invention.

FIG. 2 is a diagram showing a second constitution of the mobile terminalaccording to the first embodiment of the invention.

FIG. 3 is a flowchart showing a first operation of the mobile terminalaccording to the first embodiment of the invention.

FIG. 4 is a flowchart showing a second operation of the mobile terminalaccording to the first embodiment of the invention.

FIG. 5 is a diagram showing a first constitution of a mobilecommunication system in the first embodiment of the invention.

FIG. 6 is a diagram showing a second embodiment of the mobilecommunication system in the first embodiment of the invention.

FIG. 7 is a diagram showing a constitution of an information memory areaincluded in the mobile terminal according to the first embodiment of theinvention.

FIG. 8 is a diagram showing a first constitution of a router list in thefirst embodiment of the invention.

FIG. 9 is a diagram showing a second constitution of the router list inthe first embodiment of the invention.

FIG. 10 is a diagram showing a format of a router advertisement messagein the first embodiment of the invention.

FIG. 11 is a diagram showing a first user interface constitution of themobile terminal according to the first embodiment of the invention.

FIG. 12 is a diagram showing a second user interface constitution of themobile terminal according to the first embodiment of the invention.

FIG. 13 is a diagram showing a third user interface constitution of themobile terminal according to the first embodiment of the invention.

FIG. 14 is a flowchart showing a third operation of the mobile terminalaccording to the first embodiment of the invention.

FIG. 15 is a diagram showing a fourth user interface constitution of themobile terminal according to the first embodiment of the invention.

FIG. 16 is a diagram showing a fifth user interface constitution of themobile terminal according to the first embodiment of the invention.

FIG. 17 is a diagram of the conventional mobile terminal.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the invention will be hereinafter explained using thedrawings.

1st Embodiment

FIGS. 5 and 6 are diagrams of a mobile communication system according tothe invention.

In FIGS. 5 and 6, a link 1, to which a mobile terminal (MN) 10 and ahome agent (HA) 50 are connected, is connected to a network 2 via arouter 60.

Note that FIGS. 5 and 6 are different in that, whereas one home agent 50is connected to the link 1 in FIG. 5, two home agents 50 a and 50 b areconnected to the link 1 in FIG. 6.

In an embodiment of the invention, in a state in which the mobileterminal 10 is connected to the link 1, in response to a trigger giventhrough a user interface, the mobile terminal 10 recognizes that thelink to which it is connected is its home link and sets the home agent50 connected to the link 1 as the home agent for the mobile terminal 10.The mobile terminal 10 stores an IP address which is generated from anetwork prefix distributed by the home agent 50, as its home address.After that, the mobile terminal 10 activates mobile IP protocolprocessing referring to the information set before.

When home agent information is successfully acquired according to DHCPor the like, a user judges whether the protocol processing shall reflectthis information or not. This makes it possible for the mobile terminal10 to belong to a home agent that realizes a communication environmentdesired by the user or an application.

First, a method of acquiring home agent information upon receiving atrigger issued by the user will be explained.

In the mobile communication system shown in FIG. 5, when the user usingthe mobile terminal 10 performs setting for mobile IP of the mobileterminal 10, the user gives an instruction to the mobile terminal 10 by,for example, depressing a button included in the mobile terminal 10,changing that switch to the state ‘ON’. At this point, the mobileterminal 10 performs address information setting referring to a routerlist in which information on routers connected to the mobile terminal 10is described.

FIG. 8 is a diagram showing a constitution of the router list.

In FIG. 8, in a router list 150, at least a link layer address 151, anIP address 152, a prefix 153, and a home agent flag 154 are entered foreach router. In the mobile terminal 10 connected to the mobilecommunication system shown in FIG. 5, two entries, namely, an entry 161corresponding to the router 60 and an entry 162 corresponding to thehome agent 50 are registered. The mobile terminal 10 selects a routercorresponding to an entry 162 and whose home agent flag 154 is ‘ON’, asits home agent 50.

The mobile terminal 10 stores the IP address IP_2 of the selected homeagent 50 as the address of the home agent 50, stores Prefix_2 as theprefix of the home link, and stores an IP address generated using theprefix Prefix_2 as the home address. After that, when the mobileterminal 10 carries out mobile IP protocol processing, the mobileterminal 10 refers to the IP address and the home address of the homeagent 50 stored above.

In the mobile communication system shown in FIG. 6, the mobile terminal10 has the router list 150 shown in FIG. 9. An entry 161 correspondingto the router 60, an entry 162 corresponding to a home agent 50 a, andan entry 163 corresponding to a home agent 50 b are registered in therouter list 150. In this case, since plural home agents 50 are connectedto the link 1, the mobile terminal 10 can determine whether all of theserouters are selected, plural routers are selected, or one router isselected from among these routers.

When the mobile terminal 10 selects all the routers as its home agents,the mobile terminal 10 selects the entries 162 and 163 whose home agentflag 154 is ON. In other words, the mobile terminal 10 selects the homeagents 50 a and 50 b as the home agents for the mobile terminal 10. Themobile terminal 10 stores IP addresses of the home agents 50 a and 50 b,the prefixes of the home links, and the home addresses, according to theprocedure explained above.

When the mobile terminal 10 selects plural home agents, it is possibleto select a more suitable home agent 50 by making it possible to furtherenter a home agent preference 155 in the router list 150. In otherwords, the mobile terminal 10 selects a home agent having a home agentpreference equal to or higher than a fixed value. For example, when themobile terminal 10 selects a home agent having a home agent preferenceequal to or higher than ‘1’, the home agents 50 a and 50 b correspondingto the entries 162 and 163 are selected as home agents for the mobileterminal 10. Note however that the mobile terminal 10 may select pluralhome agents 50 at random, not referring to the home agent preference155.

When the mobile terminal 10 selects one home agent, the mobile terminal10 uses the home agent preference 155 in the same manner. For example,the home agent preference 155 indicates a preference in selecting thehome agent 50 for the mobile terminal 10. The home agent preference 155is set in accordance with the state of processing load, apparatusperformance, the preferences of the administrator, and/or the like. Themobile terminal 10 selects the home agent 50 a corresponding to theentry 162 which has the highest home agent preference as its home agent.Note that the mobile terminal 10 may assign its home agent 50 at random,not referring to home agent preference.

The mobile terminal 10 may acquire router information from the router 60and the home agent 50 connected to the link 1 after receiving a triggerfrom the user. In other words, the mobile terminal 10 transmits one ormore router solicitation messages for acquiring router information tothe link 1, and receives router advertisement messages 200 that istransmitted from the router 60 and the home agent 50 connected to thelink 1 as a response to the router solicitation messages. Subsequently,the mobile terminal 10 updates the router list 150 and carries outprocessing for selecting a home agent by the same procedure as describedabove. Then, the mobile terminal 10 performs setting of a home linkprefix and a home address. Note that the mobile terminal 10 may applythe above processing to individual messages received without performingupdate of the router list 150.

A basic constitution of the router advertisement message 200 is shown inFIG. 10.

Router information described in the router advertisement message 200includes at least the information described in the router list 150 shownin FIGS. 8 and 9 explained above. In other words, an H flag 211 of anICMPv6 router advertisement 210 corresponds to the home agent flag 154,a prefix field 221 of a prefix information option 220 corresponds to theprefix 153 and the IP address 152, and a home agent preference field 231of a home agent information option 230 corresponds to the home agentpreference 155. Although not shown in the figure, it is possible toacquire a link layer address 151 by adding an option in which a linklayer address is entered.

When the mobile terminal 10 operates as a mobile router, the mobileterminal 10 regards only home agents whose R flag 232 indicating thatthe home agent supports mobile routers is ‘ON’ in the routeradvertisement message 200 received, as objects of selection.Consequently, since a home agent not supporting mobile routers is neverselected, re-search for a home agent is not performed. Since home agentsselected support mobile routers, it is possible to prevent a packet frombeing lost during packet transmission or reception to and from a mobileterminal connected to a mobile network routed by the mobile router.

In this case, an MR (Mobile Router) Capability Column 156 may beprovided in the router list 150 in order to distinguish a home agentsupporting mobile routers and a home agent not supporting mobilerouters. This makes it possible to reduce the processing work load ofthe home agent supporting mobile routers by switching connection to ahome agent not supporting the mobile router function when the mobilerouter changes its operation to a simple mobile terminal later.

And when a home agent supporting mobile routers is assigned pluralmobile routers, resources need not be allocated to those mobile routers,and it is possible to make use of the resources which are thereby freedby simple mobile terminals for the packet transfer or other operationsfor the mobile routers registered. This makes it possible for a homeagent to process communication traffic for the mobile routers stably,which tends more than one for the simple mobile terminals.

Note that, in the embodiment described above, the setting method forresponding to a trigger which is generated by depressing the buttonincluded in the mobile terminal 10 to bring the switch into the state‘ON’ is explained. However, it is also possible to carry out the settingduring the period in which the button is being depressed or the periodin which the toggle switch is being in the state ‘ON’. In particular,when the selection of a home agent and the setting for informationregarding the home agent are performed merely using the routeradvertisement messages 200 received during the period, it is possible tomake unnecessary a timer to set a waiting limit for completion ofreception of the router advertisement messages 200, which is needed forthe case in which the setting is performed in response to a trigger.

Next, a constitution and an operation of the mobile terminal 10according to the invention will be explained using the drawings.

FIGS. 1 and 2 are diagrams of the mobile terminal 10 according to theinvention.

In FIG. 1, an L1/2 processing unit 11 transmits and receives frames toand from the link 1 and carries out processing of layer 1 and layer 2.An L3 processing unit 12 performs processing of layer 3, for example,Internet protocol (IP) processing. A higher layer processing unit 13 ishigher in order than the layer 3 and performs control for applications,session management, and the like. Note that the L1/2 processing unit 11corresponds to the transmission unit and the receiving unit in theinvention.

A user judgment acquiring unit 17 acquires a trigger indicatinginformation setting timing from a user interface unit 18. An informationsetting unit 16 performs control for setting information on the validhome agent in an information memory unit 15 in accordance with controlby the user judgment acquiring unit 17. Note that the user interfaceunit 18 corresponds to the input unit and the display unit according tothe invention.

A mobile IP processing unit 14 carries out standard mobile IP protocolprocessing in cooperation with the L3 processing unit using home agentinformation stored in the information memory unit 15.

The mobile terminal 10 shown in FIG. 2 further includes an L1/2processing unit 19 rather than the L1/2 processing unit 11, and operatesas a mobile router. Note that even the mobile terminal 10 may have aconstitution including plural L1/2 processing units 11, 19 and more.

Processing for setting the valid home agent in the mobile terminal 10constituted as described above will be explained in detail using FIG. 3.Note that the operation explained below is identical in both the mobileterminal shown in FIG. 1 and that in FIG. 2.

First, when a user depresses a setting button or the like, the userjudgment acquiring unit 17 receives a trigger indicating setting timingfrom the user interface unit 18 (S101). Then, the user judgmentacquiring unit 17 notifies the information setting unit 16 of thetrigger.

The information setting unit 16 initializes a variable Count_HA with avalue ‘0’ which is for managing the number of home agents in thefollowing processing (S102). Subsequently, the information setting unit16 refers to a router list managed by the L3 processing unit 12 andperforms the selection of the home agent 50 and the setting ofinformation such as the home agent address, as follows. First, forrespective entries registered in the router list 150 (S103), theinformation setting unit 16 checks whether the home agent flag (H flag)154 is ON (S104). When the home agent flag 154 is not ON (is OFF), theinformation setting unit 16 returns to step S103 and starts theprocessing for the next entry until no unprocessed entry is left.

When the home agent flag (the H flag) 154 is ‘ON’ in step S104, theinformation setting unit 16 judges whether the entry shall be selected(S105). For example, the information setting unit 16 judges whether theentry has a higher preference (see the home agent preference 155 of therouter list 150) with respect to the home agent 50 selected above. Whenthe entry not selected, the information setting unit 16 returns to stepS103 and starts the processing for the next entry until there are nomore unprocessed entries.

On the other hand, when the entry is selected, the information settingunit 16 sets the IP address 152 of the entry in the information memoryunit 15 as the IP address of the home agent. The information memory unit15 enters the information in the memory area managed by the informationmemory unit 15 (S106). Moreover, the information setting unit 16 setsthe prefix 153 of the entry and an IP address of the mobile terminal 10generated from the prefix 153 in the information memory unit 15 as thehome link prefix and the home address, respectively. The informationmemory unit 15 enters this information in the memory area it manages(S107).

The memory area managed by the information memory unit 15 is shown inFIG. 7. In FIG. 7, a home address is stored in a home address memoryarea 101, an IP address of a home agent is stored in a home agentaddress memory area 102, and a prefix of a home link is stored in a homelink prefix memory area 103.

The information setting unit 16 increments the variable Count_HA formanaging the number of registered home agents (S108) and judges whetherthe number of registered home agents has reached an upper limit of thenumber of home agents to be selected (S109). When the number ofregistered home agents has not reached the upper limit, the informationsetting unit 16 returns to step S103 and starts the processing for thenext entry. However, when there is no next entry, the informationsetting unit 16 displays completion of the setting processing on theinterface 18 (S120) and transitions to the trigger waiting state in stepS101. On the other hand, when the number of registered home agents hasreached the upper limit, the information setting unit 16 transitions tostep S120. It is assumed that the upper limit value of the number ofhome agents is not necessarily equal to the total number of home agentson the link. Note that step S120 for displaying completion of settingmay be omitted.

Instead of performing the information setting for the home agents 50registered in the router list 150, it is also possible to transmit arouter solicitation message to the link 1 to which the mobile terminal10 is connected, requesting router information, and perform theinformation setting on the basis of the real-time information in therouter advertisement message responding to the router solicitationmessage. Processing in that case will be hereinafter explained usingFIG. 4.

First, when the information setting unit 16 receives a triggerindicating setting timing from the user judgment acquiring unit 17(S101), the information setting unit 16 requests the L3 processing unit12 to transmit one or more router solicitation messages. The L3processing unit 12 transmits the router solicitation messages via theL1/2 processing unit 11 connected to the link 1 (S111). Note that the L3processing unit 12 may transmit the router solicitation messages to alllinks to which the mobile terminal 10 is connected, via all L1/2processing units.

The information setting unit 16 initializes the variable Count_HA formanaging the number of home agents with a value ‘0’ (S102).

When the L3 processing unit 12 receives the router advertisement message200, the L3 processing unit 12 updates the router list 150 and notifiesthe information setting unit 16 of the update (S112).

The information setting unit 16 applies the processing in steps S104 toS108 shown in FIG. 3 to the router advertisement message 200 received.Subsequently, the information setting unit 16 judges whether the numberof registered home agents has reached the upper limit of the number ofhome agents to be selected (S109). When the number of registered homeagents has not reached the upper limit, the information setting unit 16returns to step S112 and checks for reception of the next routeradvertisement message. If there is no subsequent router advertisementmessage, the information setting unit 16 displays completion of thesetting processing on the user interface 18 (S120) and transitions tothe trigger waiting state in step S101. On the other hand, when thenumber of registered home agents has reached the upper limit, theinformation setting unit 16 transitions to step S120. It is assumed thatthe upper limit value of the number of home agents is not necessarilyequal to the total number of home agents on the link.

Note that, when the information setting unit 16 receives the routeradvertisement message 200, the L3 processing unit 12 updates the routerlist 150. Thus, the information setting unit 16 can apply the processingin steps S104 to S108 to all entries in the router list 150.

In step S105, it is also possible that the candidate home agents arepresented to the user interface 18 via the user judgment acquiring unit,and that the information setting unit 16 selects the home agentdesignated by the user. Since this makes it possible for informationsetting unit 16 to select the home agent designated by the user, it ispossible to perform communication under conditions suited to theparticular data.

A specific form of the user interface 18 with which a user gives settingtiming to the mobile terminal 10 will be explained using FIGS. 11 to 13.

FIG. 11 shows a first user interface included in the mobile terminal 10according to the invention. A display 501 and a setting button 502 whichis a soft key displayed on the display unit 501 comprise the userinterface 18.

In FIG. 11, the user selects the setting button 502 to thereby instructsetting timing. The user judgment acquiring unit 17 detects the settingtiming and notifies the information setting unit 16 of the settingtiming. When information setting is completed, a notice is displayed onthe display unit 501.

FIG. 12 shows a second user interface included in the mobile terminal 10according to the invention. The display unit 501 and a setting button503 comprise the user interface 18.

In FIG. 12, the user depresses the setting button 503 to thereby specifysetting timing. The user judgment acquiring unit 17 detects the settingtiming and notifies the information setting unit 16 of the settingtiming. When information setting is completed, a notice is displayed onthe display unit 501.

FIG. 13 shows a third user interface included in the mobile terminal 10according to the invention. A setting switch 504 is the user interface18.

In FIG. 13, the user transitions the setting switch 504 to an state ‘ON’to thereby instruct setting timing. The user judgment acquiring unit 17detects the setting timing and notifies the information setting unit 16of the setting timing. When information setting is completed, a noticeis displayed on the display unit 501. Note that the user may transitionthe setting switch 504 to an state ‘OFF’ to thereby specify settingtiming.

The setting of a home agent carried out by the information setting unit16 may be limited to be performed only in the period in which thesetting button 503 is selected, the period in which the setting button504 is depressed, or the period in which the setting switch 504 istransitioned to either the state ‘ON’ or ‘OFF’.

Moreover, the display for notifying completion of information settingmay be performed on a section other than the display unit 501. Forexample, completion of information setting may be displayed byturning-on, flashing, turning-off, and the like of a not-shownindicator.

Note that, other than acquiring a trigger from the user interface 18,the user judgment acquiring unit 17 may acquire a trigger from anot-shown processing unit that controls the entire mobile terminal 10.For example, the user judgment acquiring unit 17 may carry out thesetting method explained above on receiving a trigger which norifies anew connection of the mobile terminal 10 to the link 1 has beenconnected.

Next, an operation for setting home agent information, which isperformed when the mobile terminal 10 acquires home agent informationaccording to the DHCP or the like from a network to which the mobileterminal 10 is connected, will be explained.

FIG. 14 is a flowchart of the processing for setting home agentinformation.

In FIG. 14, when the L3 processing unit 12 acquires a DHCP message(S201), the L3 processing unit 12 transfers the DHCP message to theinformation setting unit 16 after carrying out the processing thatshould conventionally be applied to the DHCP message. The informationsetting unit 16 extracts home agent information described in the DHCPmessage (S202).

Subsequently, the information setting unit 16 judges whether the homeagent information acquired is the same as the home agent informationwhich is set in the information memory unit 15 presently and which isused for mobile IP protocol processing; that is, information of thevalid home agent (S203). When the acquired home agent information is thesame as the valid home agent information, the information setting unit16 ends the processing. In the comparison of the home agent information,the information setting unit 16 may judge that the pieces of home agentinformation are identical when addresses of home agents thereof coincidewith each other and home link prefixes thereof coincide with each other.Alternatively, the information setting unit 16 may judge whether thepieces of home agent information are identical taking into account otherkinds of information.

On the other hand, when it is judged that the acquired home agentinformation is different from the valid home agent information, theinformation setting unit 16 transfers the acquired information to theuser judgment acquiring unit 17. The user judgment acquiring unit 17displays the acquired information on the user interface 18 (S204).

The user interface unit 18 can present the acquired information to theuser with, for example, user interfaces shown in FIGS. 15 and 16. InFIG. 15, on a terminal screen having the display unit 501, the userinterface unit 18 indicates, with a dialog 505, that home agentinformation different from home agent information already set andvalidated is acquired and suggests that the user judge whether to switchto a new home agent.

When the user inputs user judgment by pressing a button 506 of ‘YES’ or“NO”, the user judgment acquiring unit 17 acquires the user judgment.The user judgment acquiring unit 17 checks whether the user input is‘YES’, that is, whether the user judgment acquiring unit 17 is given acommand to switch to a new home agent from the user interface unit 18(S205). When the user judgment acquiring unit 17 is commanded to switch(the user input is “YES”), the user judgment acquiring unit 17 notifiesthe information setting unit 16 of the user input. In response to this,the information setting unit 16 sets the acquired information in theinformation memory unit 15, whereby the home agent is switched (S206).After this, the mobile IP processing unit 14 executes mobile IPprocessing using the set information.

On the other hand, when the user inputs ‘NO’ and the user judgmentacquiring unit 17 is notified that the acquired information is not to beused, the user judgment acquiring unit 17 also notifies the informationsetting unit 16 of that effect. However, although the informationsetting unit 16 stores the acquired information in the informationmemory unit 15 (S207), the information setting unit 16 ends theprocessing without switching the home agent. This is for the purpose ofusing the home agent information for later operations.

Further, as indicated by a terminal display image shown in FIG. 16, instep S205, the information setting unit 16 acquires all pieces of homeagent information held by the information memory unit 15 already andpresents, using a dialog 505, the home agent information to the usertogether with home agent information acquired anew. The user can alsoselect a desired home agent by pressing any one of buttons 507. In thiscase, when the user judgment acquiring unit 17 acquires a result of theselection by the user, the user judgment acquiring unit 17 notifies theinformation setting unit 16 of the result. When the home agent selectedis a new home agent, the information setting unit 16 sets the acquiredhome agent information in the information memory unit 15. When the homeagent selected by the user is a home agent already held by theinformation memory unit 15, the information setting unit 16 designatesthe information (S206).

Note that, the user may be allowed to select plural home agents on thedialog so that the user can select plural home agents. In this case, itis also possible to constitute a mobile terminal such that anapplication selects the transmission source address, that is, the homeaddress, by which to perform communication, and the home agent isselected without intervention of user judgment.

In this way, the user can select not only a home agent provided from anetwork but alternatively can select a different home agent appropriateat a particular time and thus be served by that home agent. For example,when the user performs business communication at the time of a businesstrip, the user can select a home agent at the user's office and thus beserved by that home agent. When the user performs private mailtransmission or Web access, the user can select a home agent of an ISPand thus be served by that home agent. This makes it possible to preventa mobile terminal from automatically setting a home agent andtransmitting confidential data without encrypting the confidential data.Thus, the user can use the mobile terminal to transmit important datawhile keeping confidentiality through an encryption path and transmitother data at high speed. In this way, it is possible to use a homeagent suitable for the situation of the user or the application. Thus,it is possible to improve convenience of the mobile terminal.

When, for example, a home agent is set in a small network environmentsuch as a home network, the DHCP does not provide home agent informationin some cases. At this time, a mobile terminal can extract informationconcerning home agents located on the link from a router advertisementmessage and, then, select and set a home agent, to which the mobileterminal belongs, from among the home agents. Moreover, at this time,the mobile terminal collects home agent information from the routeradvertisement message only when a trigger from the user is inputted.This makes it possible to prevent a waste of resources of the mobileterminal compared with the case in which home agent information iscollected steadily.

As described above, according to this embodiment, when the mobileterminal acquires home agent information such as an address of a homeagent, which is basic information for activating mobile IP protocolprocessing, the mobile IP protocol processing using the home agentinformation acquired starts upon an instruction of the user. This makesit possible to perform communication that satisfies requirements desiredby the user or the application. In addition, since the mobile terminalautomatically acquires home agent information on a link with timingspecified by the user, the work burden on the user for making settingsis reduced and convenience is improved.

INDUSTRIAL APPLICABILITY

As described above, the invention is useful for a mobile terminal or thelike in which a mobile IP protocol is operable. The invention issuitable for setting of the home agent information which isindispensable for continuing communication, even if the mobile terminalor the like move on the Internet.

1. An address information setting method comprising: a step of detectinga trigger from a user; a step of selecting a home agent to manage amobile terminal from among routers to which the mobile terminal isconnected, when the trigger is detected; a step of generating a homeaddress from the prefix distributed by the home agent selected; and astep of carrying out a mobile IP procedure using the selected home agentand the generated home address.
 2. An address information setting methodaccording to claim 1, further comprising a step of acquiring routerinformation from a network to which the mobile terminal is connected,when the trigger is detected.
 3. An address information setting methodaccording to claim 1, wherein in the selection of a home agent, a homeagent is selected from among routers whose flag indicating that it is ahome agent is on, this flag included in acquired information regardingthe routers.
 4. An address information setting method according to claim3, wherein in the selection of a home agent, from among the routerswhose flag is on, a predetermined number of routers are selectedaccording to a preference defined in advance, in order from the one withhighest priority.
 5. An address information setting method according toclaim 3, wherein in the selection step of a home agent, a home agent isselected arbitrarily from among the routers whose flag is on.
 6. Anaddress information setting method according to claim 3, furthercomprising a step of acquiring, from the user, criteria for selecting ahome agent from among the routers whose flag is on, wherein in the stepof selecting a home agent, a home agent is selected according to thecriteria.
 7. An address information setting method according to claim 1,further comprising a step of notifying the user when the selection of ahome agent is completed.
 8. An address information setting methodaccording to claim 2, wherein the selection of a home agent is performedusing router information acquired during a time period designated by theuser.
 9. A mobile terminal comprising: an input unit through which auser inputs a trigger for setting information regarding a home agent; aninformation setting unit that selects a home agent to manage the mobileterminal from among the routers to which the mobile terminal isconnected when the mobile terminal receives the trigger, and sets theaddress of the home agent and a home address which is generated from theprefix distributed by the home agent as information regarding the homeagent; and mobile IP processing means that carries out a mobile IPprocedure using the information regarding the home agent.
 10. A mobileterminal according to claim 9, further comprising: a transmitting unitthat transmits a router information request message for requestingrouter information from a network to which the mobile terminal isconnected, when a trigger from the input unit is received; and areceiving unit that receives router information response messages thatare responses to the router information request message, wherein theinformation setting unit selects a home agent to manage the mobileterminal from among the routers that have transmitted the routerinformation response messages.
 11. A mobile terminal according to claim9, wherein the information setting unit selects a home agent from amongrouters whose flag indicating that the home agent is included in therouter information of the router information response messages is on.12. A mobile terminal according to claim 11, wherein in the selection ofa home agent, from among the routers whose flag is on, a predeterminednumber of routers are selected according to a preference defined inadvance, in order from the one with highest priority.
 13. A mobileterminal according to claim 11, wherein the information setting unitselects a home agent arbitrarily from among the routers whose flag ison.
 14. A mobile terminal according to claim 11, wherein through aninput unit the user enters selection criteria for the selection of ahome agent to be performed by the information setting unit, and theinformation setting unit performs the selection of a home agent on thebasis of these criteria.
 15. A mobile terminal according to claim 9,wherein the input unit may be a soft key on a screen, a button set in amain body, or a switch set in the main body.
 16. A mobile terminalaccording to claim 9, further comprising a display unit that notifiesthe user that the setting of information regarding a home agent iscompleted.
 17. A mobile terminal according to claim 9, wherein the inputunit designates the time period in which the information regarding ahome agent is set, and the information setting unit sets the informationonly in this period.
 18. A mobile terminal according to claim 15,wherein the time period is a period in which the soft key, the button,or the switch used as the input unit is in the state ‘ON’.
 19. Anaddress information setting method according to claim 2, wherein in theselection of a home agent, a home agent is selected from among routerswhose flag indicating that it is a home agent is on, this flag includedin acquired information regarding the routers.
 20. An addressinformation setting method according to claim 19, wherein in theselection of a home agent, from among the routers whose flag is on, apredetermined number of routers are selected according to a preferencedefined in advance, in order from the one with highest priority.
 21. Anaddress information setting method according to claim 19, wherein in theselection step of a home agent, a home agent is selected arbitrarilyfrom among the routers whose flag is on.
 22. An address informationsetting method according to claim 19, further comprising a step ofacquiring, from the user, criteria for selecting a home agent from amongthe routers whose flag is on, wherein in the step of selecting a homeagent, a home agent is selected according to the criteria.
 23. Anaddress information setting method according to claim 2, furthercomprising a step of notifying the user when the selection of a homeagent is completed.
 24. A mobile terminal according to claim 10, whereinthe information setting unit selects a home agent from among routerswhose flag indicating that the home agent is included in the routerinformation of the router information response messages is on.
 25. Amobile terminal according to claim 24, wherein in the selection of ahome agent, from among the routers whose flag is on, a predeterminednumber of routers are selected according to a preference defined inadvance, in order from the one with highest priority.
 26. A mobileterminal according to claim 24, wherein the information setting unitselects a home agent arbitrarily from among the routers whose flag ison.
 27. A mobile terminal according to claim 24, wherein through aninput unit the user enters selection criteria for the selection of ahome agent to be performed by the information setting unit, and theinformation setting unit performs the selection of a home agent on thebasis of these criteria.
 28. A mobile terminal according to claim 10,wherein the input unit may be a soft key on a screen, a button set in amain body, or a switch set in the main body.
 29. A mobile terminalaccording to claim 10, further comprising a display unit that notifiesthe user that the setting of information regarding a home agent iscompleted.
 30. A mobile terminal according to claim 10, wherein theinput unit designates the time period in which the information regardinga home agent is set, and the information setting unit sets theinformation only in this period.
 31. A mobile terminal according toclaim 28, wherein the time period is a period in which the soft key, thebutton, or the switch used as the input unit is in the state ‘ON’.